<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin: 0px;
            padding: 0px;
            list-style: none;
        }
        ul{
            width: 700px;
        }
        li{
           padding: 100px;
           float: left; 
           background-color: burlywood;
           margin: 5px;
        }
    </style>
    <script src="../../js/jquery.js"></script>
</head>
<body>
    <div>
        <ul>
            <li></li>
            <li></li>
            <li></li>
            <li></li>
            <li></li>
            <li></li>
        </ul>
    </div>
    <script>
        $(function(){
            $('li').hover(function() {
                $(this).siblings().stop().fadeTo(1000,0.5);//第二个参数为透明度
            },function() {
                $(this).siblings().stop().fadeTo(1000,1);
            })
        })
    </script>
</body>
</html>